Band structure, magneto-Seebeck and magnetoresistance at the para-to ferri-magnetic transition in the Sr2FeReO6 double perovskite

Ferrimagnetic double perovskites provide a rare family of oxides where topological states might be responsible for effects at room temperature. In that respect, the effect of spin orbit coupling on the Sr 2 FeReO 6 electronic structure has been calculated. This allows to predict an induced orbital moment (+0.32 μ B ) on Re oriented in the opposite direction with respect to the spin component and substantial anomalous Hall and Nernst conductivities. Experimentally, the negative magnetoresistance and positive magnetothermopower of a Sr 2 FeReO 6 polycrystalline sample measured for temperatures below T C = 405 K demonstrate that a positive thermoelectric power factor enhancement of +20 % in 9 T is achieved in the ferrimagnetic state at 336 K. However, at that temperature, we estimate that the magnitude of the anomalous Hall conductivity does not exceed 0.1 Ω -1 .cm -1 , which is much smaller than the calculated value of 33 Ω -1 .cm -1 . The calculations likewise predict an anomalous Nernst conductivity contribution much larger than the observed experimental one, being below the resolution of our measurement. Several hypotheses are proposed to explain the discrepancies between prediction and experiments. Band structure of Sr 2 FeReO 6 double perovskite (left) taking into account spin orbit coupling, and resistivity and thermopower as a function of magnetic field. • The band structure of Sr 2 FeReO 6 with and without spin orbit coupling has been calculated. • Substantial anomalous Hall (AHC) and Nernst (ANC) conductivities are predicted. • AHC and ANC are smaller than predicted, below the resolution of the measurements. • The thermopower and electrical resistivity have been measured up to 580K, in 0 and 9T. • Negative magnetoresistance and positive magnetothermopower exist in the ferrimagnetic state.